Remote control system



Fe'b. l, 1944, H. B. DEAL.

` REMOTE CONTROL SYSTEM Filed July 23. 1941 2 Sheets-Sheet 1l Feb. 1,1944. H. B. DEAL REMOTE CONTROL SYSTEM Filed July 23, 1941 2Sheets-Sheet 2 INVENTOR HARA/10N DEAL ATTORNEY Patented Feb. 1, 1944UNITED STATES PATENT OFFICE REMOTE CONTROL SYSTEJVI'Y Harmon B. Deal,Glen Ridge, N. J.', assi'gnor to Radio Corporation of America, acorporation Application .any 2s, 1941, serial No. 403,736

10 Claims.

TheA present invention relates generally to re.- mote control systems,and more particularly to a remotecontrol. system wherein the operationof reproducer oiastandby radio receiver may be controlled from aJ remotepoint transmittingv a carrier wavev modulated by normalk ortheultra-high frequency band. In accordanceY with the presentrinvention,controlsignalswhich are preferably, though not necessarily, generated!at the broadcast vstationare utilized to modulate the carrier of`thebroadcast. stationV which is to exercise control.. Of course, ifdesired, an auxiliary special. carrier mayA bey modulated.

Ilia remote receiveristobe controlledv as. de-

scribed above, and, thestations-regular carrier is--tebemodulated..bythe control signals, it is, immaterial. whether or not.the controlling-signals are audible since the. control. signals wouldvnormally precede thestart, .and follow the termination of thespecialbroadcast. However, it isevident that, under certaincircumstances, an. in-

audible control signalisto, be preferred, as or exainplein the caserwherethere may have been in progress a program to which many people Werealready listening. and towhom an. audible con.-

trolsignal would be.y objectionable, or in cases where a certain amount`of secrecy is desirable.

Inaudibility of the, control signal may be obtained by utilizingsuper-audibleV or sub-audibleV control frequencies. Since super-audiblefrequencies would encroacnon1 adjacent broadcasty channels, sub-audiblecontrol frequencies are preierred. Another.v reason for preferring. thesub-,audible frequency bandiorv the control frequencies is because itis. immediately available since it is not beingused presently.Theaverage radio receiver.` andloud-speaker cut off belowflocycles persecond, andeven the very -best receivers with considerablebasscompensation do` nottransmt frequencies below 50 cycles persecond to anyappreciablevextent. that a band in which, controly signals will notaffect program materialbeing broadcast simul taneously, lies below50-cycles yper second Itis recognized,;of course'. that the 10Wfrequency* This.v indicatesy cut-off. of areceiver isnot abrupt, andthatthere fore. the lowest usable :frequency andeamplitude ofy thecontrol.`signals will produce'. the -least 'prozgram interference.

Inaa series of tests lwhichhave beenconducted with devices `built .inaccordance with. thegpresent. invention, it hasbeen found-thatthevamplitude oi the control signals should be .kept asn small aspossible for they reasonthat harmonics of the-control .requency-,whether originatingr-in the source or produced.in-thereceiven will 11e`in theacceptance bander the.k usual radio receiver: andlwill befaudible.The harmonicsmay be .produced inthe. receiver. by.v overload 'or b'yl-ycross-modulation of control frequencies andlprogram, .and it Vhas. beenAdetermined 1 that bothofv thesev effects .are considerably; aggravated`by large'- control. signal amplitudes.

transmitter for 1: roducing\, the controllfrequen# torV tube andmodulating. meanstor modulating# the carrierof the transmitterv withthecontroh signals. At. the` receiver, .which-isdn standbyl condition meansare provided for.receivingstlfieA modulated carrier anduti-lizing.- thederivedlsig'- nais for control. purposesf.

It. is -believed..that.-the.invention. willI belfbetter4v understood.and. its various .objects and` advanf= y tages will be more apparent..from the following detailed. description `ofk a..prefferred-embodiment:

thereof .when readv in. conjunction; with the.. atf tachedA drawings. y

In the drawings:

Figure. l illustrates` in .diagrammatid formi a suitable control..signal generating. .meanswhicli'l may be. usedY as a transmittingYstationrior.-A niodur` lating the transmitter. carrierA byy thecontrolsigf 5 nals i-in, accordance .with the presentlinventioI-nv and,l

Figure` 2 isfa diagrammatic..illustration of al'- preferred .embodiment4of arreceiver. unit adapted@ to be controlledin accordance with.receivedI consil trol signals.

Referring now more. particularly'. to.. Figure fl.

of the drawings', rtherexis .provided an electronc tube; I` whichisemployedsas; an oscillatorvvto'ge'n'e' l rate.=thevariousizdesi-redcontrol: frequencies.4 Fori' this. purpose,y a. novelAphase Vreversal circuitllarrangement ris used'f for .y providing. phasereversal between the grid andV plate oi' -theosclllatortubai I. Thephase reversal network is conn'e'cted-lbetween the r anode and-cathodeofthe-tub'and comprises capacities yil j' 8,'-and 9U and resistor`s1-40'- y andfil l: Thisfln-etworkgl also,detern'iinesthelfre-V quency ofthe generated oscillations in accordance with the values of theresistances and the condensers. Feedback between the plate and the gridis provided by a circuit 2li which connects point 26 of the phasereversing circuit to the input grid of tube I through a couplingcondenser 3. In order to avoid undesirable phase shifts in theresistance of the grid coupling circuit, ahigh resistance grid leakresistor 2 is provided.

Preferably the resistance of resistor 2 should be large as compared tothe reactance of condenser 3. Two control push buttons I and 20 areprovided. Push button 2i] acts upon depression to close a switch 2i, andthereby connects the output of the oscillator I to the ampliiier 23.Push button I5, on the other hand, acts when depressed to open switchesI7 and I8 and close switch I9. Normally resistor I3 is connected inparallel with resistor II, and, likewise, resistor I4 is connected inparallel with resistor I0. Under these conditions the net resistancebetween points 25 and 2G of the network is decreased.v This results in ahigher frequency of oscillation. Consequently, with push button I6 notdepressed, and push. button 25 depressed, control oscillations of acertain frequency are impressed upon the amplifier 23 through closedswitch 2I and conductor 22. i

.When push button I5 is depressed, the parallel resistors I3 and I4 aredisconnected from the phase shifting circuit thereby resulting in ahigher net resistance lbetween points 25 and 26 and therefore providinga lower output frequency, it being noted that the new frequency is fedto the same output amplifier 23 through conductor 22 due to closure ofswitch I9. In the condition shown, the oscillator I is operating at afrequency which is determined by resistors i0, II, I3, and I4, and theoscillations of this frequency will be impressed upon the amplifier 23upon closure of switch 2I. Hence, depression of push button 20 willimpress this control frequency upon the transmitter where it is utilizedto modulate the carrier of the transmitter in accordance with well knownpractice.

It should be noted that resistors I9, II, I3, and I4 are preferablyvariable resistors so as to permit adjustments. Also, unicontrol meansI2 is provided to adjust resistors IU and I I simultaneously, and`unicontrol means I5 is provided to permit simultaneous adjustments ofresistors I3 and I4. If-it is desired to transmit the other controlfrequency, it is only necessary to depress push button lI6 as previouslydescribed.

lFor receiving the transmitted energy there may be employed receivingapparatus such as is shown in Figure2, wherein the usual antenna system39 is. connected to the input of a radio receiver 3l which may betunable over one or more bands of frequencies if desired, it being notedthat the output of 3I comprises the audio output from the detector ofthe receiver. If `a. superheterodyne type receiver is used then theoutput is taken preferably from the second detector. The receiverportions 35, 3l, 32 and 42 are, of course, in standby condition in orderto detect the control frequencies applied over lead 45 to the relayslcontrolling the connecting means for the loud speaker 49, '19. Theaudio output of receiver 3I .is fed to a power youtput tube 42 through anetwork 32 which will be more fully described hereinafter,

,The output terminals 46, 4l of the output tube 42 are connected to atuned reed unit which includes a pair of tuned reeds 53, 59, one ofwhich reeds is responsive to one of the control frea quencies whereasthe other reed is responsive to the other of the control frequencies.The tuned reeds 53 and 59 are provided with driving electromagnets 52and 58, respectively. Tuned reed 53 is provided with a sliding weight'I9 which may be adjusted along the reed so as to tune the reed to thedesired frequency. Vibration of reed 53 causes the intermittent closureof a switch 54 which acts to connect an energizing winding 51 of adouble acting locking relay across the power supply line. Reed 59 isalso provided with a. sliding weight 8D for tuning purposes. Vibrationof reed 59 causes intermittent closure of switch 60 which in turnconnects the other energizing winding 63 of the locking relay across thepower supply line. The relay is provided with an armature 8D which isarranged to snap into either of its two positions depending upon whichone of windings 5'I and 63 is energized. In the position shown, therelay winding 5'I was energized last thereby causing the armature 89 toassume its upward position in which a pair of switches 64 and 65 aremaintained in a closed position. Under these conditions, if relay 63 isenergized, the armature Bil will snap into its downward position therebypermitting switches 64 and 65 to open and closing switches 66 and 61.

For translating the signals, there is provided a loudspeaker I9 which isconnected across switch 65 by means shown generally as a coil 49 so thatclosure of switch 65 short circuits the speaker input coil 49. In orderto provide energizing potentials for the tuned reed apparatus, a plug 69may be provided which may be plugged into any suitable socket receptacleof a power supply network. Also, a socket receptacle 63 is provided towhich may be connected any device which it is desired to control.

In order to insure that low frequency components of the program will notoperate the tuned reeds, there is provided a low pass filter composed ofelements 35, 36, 31, and 38. This filter operates to effectively cut offall frequencies above approximately 45 cycles per second. For thoseapplications where it is desirable that a loud` speaker be turned onwhere the loudspeaker is a part of the controlled receiver, an auxiliarynet-A work composed of resistor 34, condenser 39, and resistor 4I isincluded. By making the capacity of condenser 39 small so that itsreactance as compared with resistor 4I is high, this auxiliary networkoperates to pass program frequencies above say 200 cycles per second.This insures that the grid of the power output tube 42 has applied to itlow frequency components from the oscillator at the transmitting stationand also program signals, but that a band of frequencies fromapproximately 45 cycles to 200 cycles is eliminated, thus obviating thechance of low frequency components of program such as organ musicactuating the reeds. The resistor 38 is shunted across condenser 38 toprovide a direct current return path for the input grid of tube 42.

In the operation of the device shown in Figure 2, ii' the controlfrequency representative of reproducer operation is impressed uponterminal 46 from tube 42 and the circuit arrangement is in the conditionshown in Figure 2, the control energy will be fed to the energizingwinding of electromagnet 58 through the following circuit,

' terminal 46, conductor 48, closed switch 65, con- This means that theductor 59, conductor 11, closed switch 64, conductor 'I 8, winding ofmagnet 58, to terminal 41.

`control frequency is imi pressed upon` the winding" ofVN` drivingmagnet` 58: If-L r'ee'd`V 59"*isit'uned to that'particul'ar controlfrequency, it'willstartto vibrate causingintermittent closurel ofswitchf; When this happens the relajywinding 53@ will be energizedthrough the following circuit, closedlswitch 60', reed 59,- magnetcoreB-, conductor '15, one side of the'power line tonne-'terminal ofthe-power supply, then from the other terminal of thepo'wer supply tothe otherside of the powerline, resistor 14, conductor 133, the windingof relay 63, conductor 12, backto switch 60. This will cause armature 80to be pulled'4 downwardly te its' other position thereby openingswitchesGland 65 and closing switches 66 a`ndf61.y Closure of switch' 61shortcircuits the winding of relay 53 so thatthe reed-59 will stopvibrating. Closure of switch 661 will connect socket-receptacle'68Aacross the power supply line and'will thereby energizeanydesiredrcontrolled device. At the same time, the short clrcuitlacrossspeaker vcoil 45- is removediby the opening of switch E5. Hence,thespecial broadcast that was the occasion for sending the reproducecontrol frequency may be reproduced through loudspeaker' '19. Thebroadcast modulation energy is impressed across the input coil i9 of thespeaker 19 throughthe following circuit, terminal 46,conductor 43,voicel coilliconductor 5t, oondenser 5I to terminallll.

When it is desired to render the receiver reproducer ineffective theother frequency is transmitted from the transmitter thereby energizingthe relay 52 at the receiver which causesclosure of switch 5d', andenergization of relay 51, thereby bringing back the various switches tothev position shown.

While I have disclosed certain preferred embodirn'ents of. my invention,it is to be understood that the same is not limited to the detailsdisclosed and that they may be varied within the scope of the appendedclaims.

What I claim is:

l. In a signalling system of the type wherein the carrier of atransmitter is modulated by modulation signals representative of aspecial broadcast and at least two auxiliary modulation signalsrepresentative of the beginning and end of the special broadcast, asingle receiver including settable means, responsive to said auxiliarysignals in the detected output of the receiver, acting upon receipt ofone of said auxiliary signals t0 condition the receiver reproduction soas to render the special broadcast signal intelligible, said settablemeans acting upon receipt of another of said auxiliary signals tocondition the receiver reproduction so as to render the specialbroadcast signals unintelligible.

2. In a signalling system wherein means are provided at the transmittingstation for generating a plurality of different auxiliary frequencieswhich are independent of the program frequencies and lower in frequencythan the lowest program frequency to be transmitted, one of saidauxiliary frequencies being transmitted to indicate that a specialprogram transmission is about to take place and another of saidauxiliary frequencies being transmitted to indicate the end of thespecial program transmission, a receiver tuned to receive the modulatedcarrier energy transmitted from said transmitter, said receiverincluding a detector, a detected signal translating device and relaymeans, means for coupling the detector output to the relay meanscomprising a low pass lter circuit adapted to pass only frequencieswhich are below the lowest program frequency,l an additional-r circuitarranged:l tov pass only frequencies above' the lowest'lpro'gramfreequen'cies, and an operableswitchingvdeyice for connecting thetranslating device. to:` said addi;- tional circuit, wherebyl theprogramfrequencies are fed to the translating device.

3. In a receiver'ofvthe type. adapted. tocollect modulatedcarrier waveswhich have* included in the modulation at' least` one subi-audiblecontrol frequency representative'of onedesired condition of thereceiver, saidreceiver, including; meansto provide demodulation of thecollected waves thereby to provide said control frequency, and means toreproduce demodulated wave energy; the improvement which comprises a.device for controlling the effectiveness of said reproducer means,.means for controllingy the operation of said device, and meansselectively operable by said control frequency for actuatingzsaidlastcQn.- trol means, and additional means,` responsive to actuation ofsaid device control means, for ren.- dering effective an electricalcircuit.

4; In a receiver ofthe typeadapted to collect modulated carrier waveswhich have includedin the modulation atleast one sub-audib-le controlfrequency representative of one desired condition of the receiver, saidreceiver including means to provide demodulation of the collected wavesthereby to provide said control frequency, and means to reproduceldemodulated Wave energy; the improvement which comprises a device forcontrolling the effectiveness of said reproducer means, meansforcontrolling the. operationr of said device, and means selectivelyoperableby said control frequency for actuating said last control means,and additional means, responsive to actuation of said control means, forrendering saidv selectively operable means ineffective 5. In a receiverof the type adapted to collect modulated carrier waves which haveincluded in the modulation at least one sub-audible control frequencyrepresentative of one desired condition of the receiver, said receiverincluding means to provide demodulation of the collected waves therebyto provide said control frequency, and means to reproduce demodulatedwave energy; the improvement which comprises a device for controllingthe effectiveness of said reproducer means, means for controlling theoperation of said device, and means selectively operable by said controlfrequency for actuating said last control means, said selectivelyoperable means consisting of a reed tuned to said control frequency, andelectromagnetic means for vibrating said reed in response to energy ofsaid control frequency.

6. In a receiver of the type adapted to collect modulated carrier waveswhich have included in the modulation at least one sub-audible controlfrequency representative of one desired condition of the receiver, saidreceiver including means to provide demodulation of the collected wavesthereby to provide said control frequency, and means to reproducedemodulated wave energy; the improvement which comprises a device forcontrolling the effectiveness of said reproducer means, means forcontrolling the operation of said device, and means selectively operableby said control frequency for actuating said last control means, asecond means selectively operable by a different sub-audible controlfrequency included in said modulation in place of said first controlfrequency, a second means, controlling the operation of said reproducercontrol device, adapted to be actuated by said second selectivelyoperable means. x

. yr1. In a receiver of the type adapted to collect modulated carrierWaves which have included in the modulation at least one sub-audiblecontrol frequency representative of one desired condition of thereceiver, said receiver including means to provide demodulation ofv thecollected Waves thereby to provide said control frequency, and means toreproduce demodulated wave energy; the improvement which comprises adevice for lcontrolling the effectivness of said reproducer means, meansfor controlling the operation of said device, and means selectivelyoperable by said control frequency for actuating said last controlmeans, a second means selectively operable by a diierent sub-audiblecontrol frequency included in said modulation in place of said rstcontrol frequency, a second means, controlling the operation of saidreproducer control device in a sense opposed to the control of saidfirst device control means, adapted to be actuated by said secondselectively operable means.

8. In a radio signalling system including a receiver upon Whose inputterminals are applied modulated carrier Waves Whose modulation sig-`nals include at least one control frequency representative of a desiredstate of eiectiveness of the receiver, said receiver including detectionmeans for deriving energy of said control frequency from the waves, acontrol device for controlling tlie eiectiveness of the receiver, anelectromagnetic device including an energizing circuit for actuatingsaid control device, a selective reed means, tuned to said controlfrequency, for controlling the said energizing circuit, and means,responsive to said derived control frequency energy, for intermittentlycontrolling said selective means.

9. In a radio signalling system including a receiver ,upon whose inputterminals are applied modulated carrier waves whose modulation signalsinclude at least one control frequency representative of a desired stateof effectiveness of the receiver, said receiver including detectionmeans for deriving energyof said control fr equency from the Waves, acontrol device for controlling the effectiveness of the receiver, anelectromagnetic device including an energizing circuit for actuatingsaid control device, a selective means, tuned to said control frequency,for controlling the said energizing circuit, and means, responsive tosaid derived control frequency energy, for controlling said selectivemeans, and additional means, responsive to energization of saidelectromagnetic device and actuation of the control device, forpreventing operation of the means for controlling the selective means.

l0. In a radio signalling system including a receiver upon whose inputterminals are applied modulated carrier waves Whose modulation signalsinclude at least one control frequency representative of a desired stateof effectiveness of the receiver, said receiver including detectionmeans for deriving energy of said control frequency from the waves, acontrol device for controlling the effectiveness of the receiver, anelectromagnetic device including an energizing cir. cuit for actuatingsaid control device, a selective reed, tuned to said control frequency,for controlling the said energizing circuit, and means, responsive tosaid derived control frequency energy, for controlling said selectivereed, and a lter network following said detection means for preventionof transmission of modulation energy of from approximately to 200cycles.

HARMON B. DEAL.

